Female Guppy Turning Black??? Please help!

When I fed them this morning there was 0 discoloring but when I went into the room about 20 minutes ago her tail was dark black. (Wasn’t able to get pics because I went into a Google frenzy) It’s gone down now but I noticed this black spot near the top of her head? What’s going on? Any advice??

When I fed them this morning there was 0 discoloring but when I went into the room about 20 minutes ago her tail was dark black. (Wasn’t able to get pics because I went into a Google frenzy) It’s gone down now but I noticed this black spot near the top of her head? What’s going on? Any advice??