Mystery Deaths in the Tank

Need your help on some mystery deaths in my tank: I bought 2 plecos one week ago and now they’re both dead. One pleco died yesterday and the other turned up today. However, the tank mates (3 platies, 3 zebras) are just fine. So, I’m basically trying to figure out exactly what happened. One thing I noticed with the plecos was that they’d constantly hug the wall near or around the heater. Did they fry to death? Please tell me no. The only thing I can think of is the food issue. I maintained the same feed (flakes, brine shrimp, bloodworms) for the tank…instead of adding in certain foods e.g. algae wafers. I thought the plecos were doing a great job cleaning up the brown algae…but then something must have happened.

I have a 20g tank (artificial plants) with 3 platies and 3 zebras. Here are my parameters (taken today):

Temp – 78F
pH – 7.0
NH3 – 0
NO2 – 0.05

Thanks, guys.

The tank is now about 3 months old and it is well cycled. As mentioned, the 3 platies and 3 zebras are doing just fine.

The ammonia reading - taken just yesterday - is 0 (zero).

They were Trinidad Plecos. You certainly have a point about size (I was thinking of getting a bigger tank down the road). Would you recommend any smaller cats?