To some extent boots and other shoes mold to feet. To some extent the reverse is also true. It may help to try skating a little more again, before you make the decision to buy new equipment.
I don't know whether Jackson Debut boots can be heat molded in the type of oven pro shops have. If unsure, call Jackson.
If what FigureSpins said isn't enough, ask your pro shop - even a hockey store will do, if they are any good - whether or not they can do an oven heat mold. You can mold boots yourself using a handheld hair drier, if you are careful and pay attention to heat molding temperatures, but if you are uncertain about doing stuff yourself, a competent pro shop is more likely to do a good job, and the price some of them cite is reasonable.
(In general, going to the lowest bidder on matters of boot fit and other issues isn't always a good idea. Ask other experienced skaters, and coaches, what pro shops they like best, and which skate techs at each shop they like best, and be willing to drive a few hours each way if needed.)
Boots can absorb moisture, if stored in an unusually humid place. But, AFAIK, the weight of the extra water is normally insignificant, and I suspect sweat from normal human feet usually creates a more humid environment than most indoor storage environments. Perhaps the perceived increase in weight issue is more likely a matter of not being used to using ice skates, or skating-specific fitness issues.
It is obviously possible that fitness might change the shape of your feet a little, and might change your ankle bend strength as well. Not only that, but if you haven't been doing appropriate stretch exercises, the range of motion of all your joints (e.g., ankle joints, hip joints), might be less. So, even if you decide you want new boots, or if needed, new blades, you might want to give yourself more skating time again to get back in shape and flexibility, so the new fit stays right.
I like to make or modify or add my own insoles. If you add thickness (e.g., with coach tape or other cloth athletic tape) underneath the insole where the fit is loose, you can sometimes snug them up that way, though you need to be careful that it doesn't adversely affect your sideways balance. If you make the insoles extra wide in the spots where the fit is loose sideways (or you you add tape from underneath that extends next to your feet), they will come up around the sides of your feet and snug them up. Alternately, you could firmly stick good quality moleskin to the insides of the boot next to where they are loose - a somewhat temporary solution, but a lot of people use it.
I disagree with a lot of people, including people with more experience than me, about blade length. I don't think the nominal lengths have to match the lengths of the outsoles of your boots, especially on non-custom boots. (On fully custom boots, boot makers sometimes deliberately size the outsoles so most fitters will pick what they guess is the "right" length blades for your feet. But that is much less likely to be true on your off-the-shelf boots - e.g., the internal length of your boots might be significantly less than the lengths of your feet.) I think they should instead work with the anatomy of your feet - though it is true that if the insides of a specific pair of boots have more or less front-to-back tilt, the vertically projected length of the feet onto the blades will be less or more, so to that extent blade length should depend on internal boot shape. Nonetheless, my theory at least, is that, to keep your blades, you don't have to order the size of your boots to match the nominal length of the blades, but could order boots that fit you better.
I also disagree with a lot of people, including people with more experience than me, that there is only one possible place, front-to-back, to mount your blades. (Again, on fully custom boots, boot makers sometimes deliberately position the outsoles so most fitters will mount the blades in the right position, which is less likely to be true on stock boots.) If you are having trouble pointing your ankles enough to dig in a toe pick for a jump (that applies to both edge and toe jumps), you could mount the blades a little bit further back. Of course, if they are too far back, it is easier to trip your self by crossing your blades, and it can be very hard to balance and skate if what I was told to call the "sweet spot" (where the rocker curvature of the blade changes) isn't approximately below the balls of your feet. (I personally like the sweet spot slightly forwards of that). I am not a good enough jumper to guess if the position of the tails of your blades can also adversely affect jumping, but on jumps where you land on the tail, it seems like it might. What this boils down to is that optimal blade mount position (which might depend on joint flexibility), involves trade-offs, and you may want to think about whether you think a different mount position will help, and you may need to experiment. If you are not confident about remounting your blades (and it is very easy to strip the holes in leather), get a good pro shop to do it.
But again, give yourself a little more time to re-adapt first.
For that matter, If you are having trouble jumping, I wonder if it is safer at first to get back into shape before doing hard jumps, because jumps are a frequent way to injure yourself.