Mollygup,has Bubbles /blisters In Tail Fin.

[4188Barry]

Looks like molly,but with colours in it.
This one has,or had a Great orange tail.now full of bubbles within the membrain,some large ,some small..Doesnt seem to
worry or affect him,still rushing about(all Males in tank,5 off ),But one before,bubbles in dorsal fin,after little while died..

Tank size 30 Lts,has other M/gups and Two male swordtails,all seem ok
3rd of water changed three weeks.
nitrate,nitrite ph,all OK

?

 

[WILDER]

Are the bubbles beneath the skin or on top.
Any signs of flicking and rubbing, or laboured breathing.