Holy cow! I think those rir/ slw are sexlinked!
I thought that about your SLW / RIR cross when you first posted about her, Kab, but I did some research and I don't think so now. If it had been the other way (red male, silver female), then you would have had red sexlinks like you said. Based on what I'm reading, I don't think SLW boys can be used for sexlink crosses, though. If I'm understanding everything, if you cross a silver male with red females, all offspring will be silver (visually mostly white as adults).
Good info on the topic:
https://www.backyardchickens.com/t/261208/sex-linked-information
This is all genetics related to Wyandottes:
http://minifluffsrabbitry.weebly.com/wyandotte-chicken-color-genetics.html