I have a 29 gallon tank with 3 green tiger barbs, 2 regular tiger barbs, 1 bristlenose pleco and one rainbow shark. In the last 2 weeks or so i've notived one green barb and one regular barb have not grown at all since ive got them a little over a month ago, same time as i got the other barbs which are growing heathy. In fact they almost seem to be shrinking and losing color although i do see them eat and they act normal and very active just like all the others. I've read this might indicate an internal parasite? If so how would i go about treating them without a quarantine tank? 
