Using front RCA's for front and rear inputs on amp

Will using the front (L)(R) RCA's for my front and also rear L,R inputs on my amp cause any issue or signal loss? When i was fixing the pico fuse on my HU i decided to test the rca's and was getting nothing from the rear rca's but the front's were fine. Havent hooked them up in the car yet so im not 100% sure there either working or not working. So if im getting no signal from my rear rca outputs on my HU, what can i do to ensure i have a left and right signal for both front and rear channels on my 4channel amp?

 

If i use a splitter to turn 2 rca's into 4, will i suffer power loss? =( helpp

 

ty, now i wont be concerned until saturday, you sir have caused me much relief