I have a rather weird problem here. I'll start at the beginning.
The version is 1.7.10, reason for that is mods. Another detail is that I used universal version of forge, there are reasons for that and I cannot use an installer in any way.
The version I used was the recommended version downloaded from files.minecraftforge.net, which is 10.13.4.1558. It worked fine with all of my 42 mods. Then I decided to add another mod (RTG if that matters). When I did that, it started telling me at Minecraft startup that
That's weird, isn't it? I already had that version installed. So I decided that the problem is in the mod, and deleted it. After some time (without adding any more mods) I've added another mod (Ex Futurum if you need that). And guess what? It started doing the same thing. Minimum version required is 10.13.4.1558. I deleted the mod, and tried adding another random mod, and after testing about 5 different mods they worked fine. The problem was only with these two. I don't know if there are any other mods with that problem.
What I also tried to do is installing the newest version of Forge instead, which is 10.13.4.1614. Absolutely no differences occured. And yes, I did re-install both Minecraft and Forge from scratch in both cases.
I could live without those two mods, but I really want them, and it seems that I won't be able to do anything about this problem without your support, which would be exceptionally highly appreciated.
P.S. Sorry for my English if there's anything wrong with it, I'm not native English-speaking.
Thanks, ViAik