Hello and welcome to the forum!
The first helmet you show in your photos on the left side view was worn by a Prussian Guard Regiment. It is for a One Year Volunteer or a possible non-commissioned officer helmet. It is not a helmet from Reuss.
The second helmet that you show on the far right view of your photos posted here is a Model 1915 Prussian enlisted man's helmet. It appears that part of the leather liner is missing.
Can you possibly show views of all 4-sides of each helmet, and please show the entire view of the helmet in each of your photos?
For example, a full left side view, a full right side view, and a full back of the helmet view? Please make certain to show the entire view of the helmet in each photo, and do not crop off the top part of the spike, or negect to show the full underside of the visors on each helmet. It is important to see the full views in order to assess the condition of each helmet.
Thanks,
Alan