Not sure if these are something to be concerned about, but thought I'd report them in any case.
sir_model = @reaction_network SIR begin
c1, s + i --> 2i
c2, i --> r
end c1 c2
p = (0.1/1000,0.01)
u0 = [999.,1.,0.]
tspan = (0.,250.)
julia> @code_warntype ODEProblem(sir_model,u0,tspan,p)
Body::Any
34 1 ─ %1 = invoke DiffEqBase.:(#ODEProblem#302)($(QuoteNode(Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}()))::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, _1::Type, _2::Function, _3::Array{Float64,1}, _4::Tuple{Float64,Float64}, _5::Tuple{Float64,Float64})::Any
└── return %1
julia> @code_warntype SDEProblem(sir_model,u0,tspan,p)
Body::Any
2 1 ─ %1 = (getfield)(args, 1)::Tuple{Float64,Float64} │
│ %2 = (getfield)(args, 2)::Tuple{Float64,Float64} │
│ %3 = (Base.getfield)(rn, :g)::Function │╻ #SDEProblem#44
│ %4 = (Base.getfield)(rn, :p_matrix)::Array{Float64,2} ││┃ getproperty
│ %5 = %new(NamedTuple{(:noise_rate_prototype,),Tuple{Array{Float64,2}}}, %4)::NamedTuple{(:noise_rate_prototype,),Tuple{Array{Float64,2}}}
│ %6 = DiffEqBiological.SDEProblem::Type{SDEProblem} ││
│ %7 = invoke getfield(Core, Symbol("#kw#Type"))()(%5::NamedTuple{(:noise_rate_prototype,),Tuple{Array{Float64,2}}}, %6::Type{SDEProblem}, _2::Function, %3::Function, _3::Array{Float64,1}, %1::Tuple{Float64,Float64}, %2::Tuple{Float64,Float64})::Any
└── return %7 │
julia> @code_warntype solve(prob,EM(), dt=.01)
Body::Any
1 ─ %1 = %new(Base.Iterators.Pairs{Symbol,Float64,Tuple{Symbol},NamedTuple{(:dt,),Tuple{Float64}}}, #temp#, (:dt,))::Base.Iterators.Pairs{Symbol,Float64,Tuple{Symbol},NamedTuple{(:dt,),Tuple{Float64}}}
│ %2 = (getfield)(args, 1)::Core.Compiler.Const(EM{true}(), false) │
│ %3 = invoke DiffEqBase.:(#solve#442)(%1::Base.Iterators.Pairs{Symbol,Float64,Tuple{Symbol},NamedTuple{(:dt,),Tuple{Float64}}}, _3::Function, _4::SDEProblem{Array{Float64,1},Tuple{Float64,Float64},true,Tuple{Float64,Float64},Nothing,SDEFunction{true,SIR,getfield(Main, Symbol("##9#25")),LinearAlgebra.UniformScaling{Bool},Nothing,Nothing,Nothing,Nothing,Nothing,Nothing,Nothing,Array{Symbol,1},Nothing},getfield(Main, Symbol("##9#25")),Nothing,Array{Float64,2}}, %2::EM{true})::Any
└── return %3
julia> @code_warntype JumpProblem(dprob,Direct(),sir_model)
Body::Any
7 1 ─ %1 = invoke DiffEqBiological.:(#JumpProblem#45)($(QuoteNode(Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}()))::Base.Iterators.Pairs{Union{},Union{},Tuple{},NamedTuple{(),Tuple{}}}, _1::Type, _2::DiscreteProblem{Array{Float64,1},Tuple{Float64,Float64},true,Tuple{Float64,Float64},DiscreteFunction{true,getfield(DiffEqBase, Symbol("##270#271")),Nothing},Nothing}, _3::Direct, _4::SIR)::Any
└── return %1