Are you talking about the lighter areas on his head?
If so, they look like they could be one of two things: either they are spots where he's been nipped/injured and his scales have been removed or they are the beginnings of an external bacterial infection (like that which causes finrot).
When did they appear? Have they grown in size at all? What's your tank's temp.? Have you changed that recently? What are your water parameters?
I see you have another, apparently male, dwarf in with this one so nipping isn't out of the question. If that is the case, just watch the fish closely and make sure you keep the water extra clean by doing some small, frequent water changes. It may also help to add a half dose of melafix or a little salt (if you don't have any salt-intolerant fish). Make sure you don't cause him any stress though. Hopefuly, he won't get a secondary infection and will heal nicely.
If what he has is bacterial, however, you need to begin by making sure the water's extra clean and then lower the temperature of the tank (very gradualy) so that it's not above 76 deg F. That'll slow the infection. Then get an anti-finrot and fungus med such as that made by interpet (that particular one - treatment number 8 - has worked well for me in the past) and follow the instructions for the dosage. At the moment, at least from the pic, I can't tell whether this is bacterial or not so I would give it some time and only treat once you're certain. If you can tell, then go ahead with the treatment.
There is one last possibility - that these are the beginnings of ulcers. How long have you had your gouramies? Hopefuly this isn't what he has but, if it is, you'll need to isolate him and treat with an antibiotic. There realy isn't a way of telling from that pic at the moment so you'll either have to wait until it gets worse or treat regardless. IMO, it would be best to wait and not put him under unecessary stress when it may just be a few missing scales.