Hi all. I'm new to tropical fish!! Got 4 platies. All OK for 2 weeks. Week 3 we introduced 2 Neons. Both died within 2 days. Water checked, all OK. Got 2 new Honey Gourami. All OK for 4 days. 2 platies now dead and the other 2 look dodgy. Any ideas?? Have a picture of 1 of the platies. Looks...