Keep an eye on it. The leaking is not normal, but the sizzling/boiling is so long as you aren't noticing hot batteries.
Not getting a full charge on your batteries then discharging them (either fully or partially) is also very hard on batteries and will shorten their service life. The reason I mention this is that you said your charger is 2A output. I'm not sure how often you fish, but it will take quite a while to charge an even partially discharged deep cycle battery at 2 amps. For ease of explanation, think about this. If you have a 100 amp hour battery and it is 50% discharged, then you have to restore 50 amp hours to bring it back to full charge. So, hypothetically we have 100% charger/battery efficiency with no loss: 50Ah/2 Amps = 25 hours charge time minimum.
Good luck